Jet Propulsion Laboratory;
California Institute of Technology;
Instirute of Planetary Research;
Germany;
German Aerospace Center (DLR);
Viterbo;
Duesseldorf;
Department of Ecological and Biological Sciences (DEB) Largo dell'Universita snc 01100 Viterbo (Italy);
Jet Propulsion Laboratory;
Italy;
Cologne;
Berlin;
USA;
Madrid;
Institute of Aerospace Medicine;
Pasadena;
University of Tuscia;
Torrejon de Ardoz;
Spain;
Spanish Aerospace Research Establishment-INT A;
Department of Earth Observation;
California;
Department of Ecological and Biological Sciences;
Institut fuer Botanik;
Heinrich-Heine-Universitaet;
Cryptoendolithic microbial communities and epilithic lichens have been considered as appropriate candidates for the scenario of lithopanspermia, which proposes a natural interplanetary exchange of organisms by means of rocks that have been impact ejected from their planet of origin. So far, the hardiness of these terrestrial organisms in the severe and hostile conditions of space has not been tested over extended periods of time. A first long-term (1.5 years) exposure experiment in space was performed with a variety of rock-colonizing eukaryotic organisms at the International Space Station on board the European EXPOSE-E facility. Organisms were selected that are especially adapted to cope with the environmental extremes of their natural habitats. It was found that some- but not all-of those most robust microbial communities from extremely hostile regions on Earth are also partially resistant to the even more hostile environment of outer space, including high vacuum, temperature fluctuation, the full spectrum of extraterrestrial solar electromagnetic radiation, and cosmic ionizing radiation. Although the reported experimental period of 1.5 years in space is not comparable with the time spans of thousands or millions of years believed to be required for lithopanspermia, our data provide first evidence of the differential hardiness of cryptoendolithic communities in space.
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